Pressure sensitive adhesive for photoactive or photographic substrates

ABSTRACT

A method is provided for photographic developing using a roll of photographic paper. A photographic image is formed on the paper, and the image-containing portion of the paper cut from the roll of paper. The improvement comprises the end of the roll of paper being initially maintained in place by means of a pressure sensitive adhesive tape comprised of a polyisobutylene-or polybutene-based pressure sensitive adhesive on a backing layer, with the tape being removed prior to the roll being used as a substrate for the photographic image. The combination of a roll of photographic paper whose free end is held in place by the pressure sensitive adhesive is also provided.

This Non-provisional application claims priority under 35 U.S.C. § 119(e) on U.S. Provisional Application No. 60/485,107 filed on Jul. 8, 2003, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

In commercial photofinishing, photoactive or photographic paper is employed onto which a customer's images are printed. Photographic paper rolls are generally mounted onto cardboard rolls which are in turn mounted on a spindle in the printer. The paper is advanced through the printer, the image is printed onto the paper, and the exposed portion of the paper cut to size.

In order to inhibit the end of the paper roll from becoming loose prior to being mounted on the spindle, it has been the custom to attach the end of the roll to the rest of the roll by means of a small portion of pressure sensitive adhesive tape. Once being selected for use in the printer, the tape is removed and the roll mounted in the printer.

However, depending upon the chemistry of the particular pressure sensitive adhesive employed and the degree of aggressiveness of the adhesive, removal of the tape has been seen to cause blisters on the surface of the paper itself. Also, the chemistry of the adhesive itself has frequently been found to react with components of the photographic film. This results in a need to trim the roll to remove portions rendered unacceptable due to the above.

It is thus an object of the present invention to provide a method for stabilizing the ends of the roll of the photographic paper which avoids the above problems.

It is also an object of the present invention to provide a method for adhering the end of the roll of photographic paper by means of a pressure sensitive adhesive tape which is non-reactive with the paper.

It is also an object of the present invention to provide a method for adhering the end of the roll of photographic paper by means of a pressure sensitive adhesive tape which exhibits tailored tack values so that damage to the paper is minimized.

As a result of the present invention, there is thus provided a pressure sensitive adhesive tape which meets the above objectives. The pressure sensitive adhesive tape of the present invention is comprised of a polyisobutylene-or polybutene-based pressure sensitive adhesive. It has been found that such a pressure sensitive adhesive has particular suitability for use with photographic paper rolls, while avoiding the above-discussed disadvantages of the prior art.

There is also provided a method for photographic developing using a roll of photographic paper, wherein a photographic image is formed on said paper, and said image-containing portion of said paper being cut from said roll of paper, the improvement wherein the end of said roll of paper is initially maintained in place by means of a pressure sensitive adhesive tape comprised of a polyisobutylene- or polybutene-based pressure sensitive adhesive on a backing layer, with said tape being removed prior to said roll being used as a substrate for said photographic image.

DETAILED DESCRIPTION OF THE INVENTION

The pressure sensitive adhesive of the present invention is comprised of polyisobutylenes, polybutenes or mixtures thereof in order to yield the balance of adhesive properties required for the present invention. The pressure sensitive adhesive is preferably comprised of a high molecular weight fraction and a low molecular weight fraction of polyisobutylenes, polybutenes, or mixtures thereof to enhance the pressure sensitive characteristics of the composition.

The high molecular weight fraction of either the polyisobutylene or polybutene may be characterized by a molecular weight M_(W) in the range of 1,000,000 to 1,800,000, and a molecular weight M_(n) in the range of from 500,000 to 900,000. The high molecular weight fraction is in the form of a rubber-like elastic mass.

The low molecular weight fraction of either the polyisobutylene or polybutene may be characterized by a molecular weight M_(W) of up to about 27,000 and a molecular weight M_(n) of up to about 10,000. The low molecular weight fraction is in the form of an oligomer.

The weight ratio of low molecular weight fraction to high molecular weight fraction ranges from about 20:80 to 60:40, and preferably from about 30:70 to 50:50. Essentially, sufficient low molecular weight polyisobutylene or polybutene is admixed with the high molecular weight polyisobutylene or polybutene to yield a polymer mixture having pressure sensitive adhesive properties. High and/or low molecular weight polyisobutylenes may be used with high and/or low molecular weight polybutenes without detriment.

The low and high molecular weight fractions can be admixed together in the presence of a suitable solvent such as heptane, toluene or hexane. It is preferable to use a medical grade solvent to minimize the presence of impurities in the solvent. The respective components can be admixed with any conventional mixing apparatus, such as a twin screw extruder. Various fillers may be incorporated into the admixture, with the proviso that the filler does not interfere with the photoactivity of the paper.

In order to minimize interference with the photoactivity of the paper or other substrate, it is desirable to minimize or avoid entirely the presence of free monomers, free acrylic acids, and free silicones (not otherwise 100% crosslinked) in the adhesive composition. It is has been desirably found that the use of a pressure sensitive adhesive comprised of polyisobutylene or polybutene components (or mixtures thereof) avoids such undesirable interactions due to the lack of functionality of the component materials. The polyisobutylene and polybutene components have also been found to provide satisfactory adhesive characteristics over the temperature range within which such photographic substrates are used. Preferably, the adhesive composition consists essentially of the polyisobutylene, polybutene or mixture thereof, and most preferably, the adhesive composition consists entirely of such components. Components other than polyisobutylene or polybutene may be present in minor amounts to the extent that they do not cause undesirable interaction with the photoactivity of the substrate.

Once formed, the adhesive composition can be applied to a suitable backing or release liner. Once applied, residual solvent (if any) which may be present may be removed by conventional means such as by application of elevated temperatures or reduced pressure. For example, temperatures in the range of from 180° F. to 280° F. can be used to remove residual solvent.

Exemplary backing materials used in the production of such a product include but are not limited to flexible and inflexible backing materials conventionally employed in the area of pressure sensitive adhesives, such as creped paper, kraft paper, fabrics (knits, non-wovens, wovens), foil and synthetic polymer films such as polyethylene, polypropylene, polyvinyl chloride, poly(ethylene terephthalate) and cellulose acetate, as well as glass, ceramics, metallized polymer films and other compatible sheet or tape materials.

It is sometimes advantageous to employ an adhesion promoter on the backing layer prior to application of the adhesive layer to promote adhesion of the adhesive to the backing layer. This has been found to be particularly advantageous when a polyester backing layer is used, so that the adhesion of the adhesive to the polyester backing layer is enhanced. Exemplary adhesion promoting materials which can be employed include but are not limited to functionalized olefinic materials.

It has been found, when a metal chelate is used as the adhesion promoting layer, that the static dissipative properties of the adhesive tape are significantly enhanced. This has been found to be a distinct advantage with respect to the film-imaging environment, as excessive static can adversely affect the imaging process.

In use, the pressure sensitive adhesive tape of the present invention may be used to attach the free end of the paper roll to the adjacent layer of paper on the roll for purposes of storage and transport of the roll. When it is desired to use the roll in the formation of a developed paper, the tape may be easily removed from the roll without the photographic chemistry of the paper on the roll being adversely affected, or the physical integrity of the paper layer being damaged. 

1. In a method for photographic developing using a roll of photographic paper, wherein a photographic image is formed on said paper, and said image-containing portion of said paper being cut from said roll of paper, the improvement wherein the end of said roll of paper is initially maintained in place by means of a pressure sensitive adhesive tape comprised of polyisobutylenes, polybutenes, or mixtures thereof on a backing layer, with said tape being removed prior to said roll being used as a substrate for said photographic image.
 2. The method of claim 1, wherein said pressure sensitive adhesive tape comprises a polyester backing layer.
 3. The method of claim 1, wherein a binder coating is applied between said backing layer and said pressure sensitive adhesive.
 4. The method of claim 3, wherein said binder coating has antistatic properties.
 5. The method of claim 1, wherein said adhesive is comprised of a mixture of high and low molecular weight polyisobutylene components present in ratios sufficient to result in a pressure sensitive adhesive.
 6. The method of claim 1, wherein said adhesive is comprised of a mixture of high and low molecular weight polybutene components present in ratios sufficient to result in a pressure sensitive adhesive.
 7. The method of claim 5, wherein the high molecular weight fraction may be characterized by a molecular weight M_(w) in the range of 1,000,000 to 1,800,000, and a molecular weight M_(n) in the range of from 500,000 to 900,000, and the low molecular weight fraction may be characterized by a molecular weight M_(w) of up to about 27,000 and a molecular weight M_(n) of up to about 10,000.
 8. The method of claim 6, wherein the high molecular weight fraction may be characterized by a molecular weight M_(w) in the range of 1,000,000 to 1,800,000, and a molecular weight M_(n) in the range of from 500,000 to 900,000, and the low molecular weight fraction may be characterized by a molecular weight M_(w) of up to about 27,000 and a molecular weight M_(n) of up to about 10,000.
 9. The method of claim 5, wherein the weight ratio of low molecular weight fraction to high molecular weight fraction ranges from about 20:80 to 60:40.
 10. The method of claim 6, wherein the weight ratio of low molecular weight fraction to high molecular weight fraction ranges from about 20:80 to 60:40.
 11. The method of claim 1, wherein said pressure sensitive adhesive is free of free monomers, acrylic acids or silicone polymer components.
 12. The method of claim 1, wherein said pressure sensitive adhesive comprises a mixture of polyisobutylenes and polybutenes.
 13. In combination with a roll of photographic paper, a pressure sensitive adhesive tape maintaining a free end of said paper roll in place against said roll of paper, the improvement wherein said adhesive tape is comprised of a pressure sensitive adhesive comprised of polyisobutyenes, polybutenes, or mixtures thereof on a backing layer.
 14. The combination of claim 13, wherein said polyisobutylene adhesive is comprised of a mixture of high and low molecular weight polyisobutylene in a ratio sufficient to result in pressure sensitive adhesive properties.
 15. The combination of claim 13, wherein said polybutene adhesive is comprised of a mixture of high and low molecular weight polybutene in a ratio sufficient to result in pressure sensitive adhesive properties.
 16. The combination of claim 14, wherein the high molecular weight fraction may be characterized by a molecular weight M_(w) in the range of 1,000,000 to 1,800,000, and a molecular weight M_(n) in the range of from 500,000 to 900,000, and the low molecular weight fraction may be characterized by a molecular weight M_(w) of up to about 27,000 and a molecular weight M_(n) of up to about 10,000.
 17. The combination of claim 15, wherein the high molecular weight fraction may be characterized by a molecular weight M_(w) in the range of 1,000,000 to 1,800,000, and a molecular weight M_(w) in the range of from 500,000 to 900,000, and the low molecular weight fraction may be characterized by a molecular weight M_(w) of up to about 27,000 and a molecular weight M_(n) of up to about 10,000.
 18. The combination of claim 14, wherein the weight ratio of low molecular weight fraction to high molecular weight fraction ranges from about 20:80 to 60:40.
 19. The combination of claim 15, wherein the weight ratio of low molecular weight fraction to high molecular weight fraction ranges from about 20:80 to 60:40.
 20. The combination of claim 13, wherein said pressure sensitive adhesive is free of free monomers, acrylic acids or silicone polymers.
 21. The combination of claim 13, wherein a binder coating is present between said backing layer and said pressure sensitive adhesive.
 22. The combination of claim 21, wherein said binder coating has antistatic properties.
 23. The combination of claim 13, wherein said backing layer is a polyester layer. 